A lead locking device has a lead insertion member having a proximal end and a distal end and has a lead engaging assembly. The lead insertion member defines a lumen extending along a longitudinal axis between the distal end and the proximal end of the lead engaging assembly. A mandrel disposed in the lumen of the lead engaging assembly extends along substantially the entire length of the lumen and protrudes beyond the most proximal end of the lead insertion member. The mandrel includes a distal portion in slidable contact with at least a portion of the lead engaging assembly. The lead engaging assembly has a first configuration while being inserted into a lumen of a lead and a second configuration while engaging the lead from within the lumen of the lead. The lead engaging member has at least two expansion jaws that, in the first configuration, define a substantially cylindrical body. The expansion jaws translate radially outwardly from the longitudinal axis to engage the lumen of the lead when in the second configuration.